Before being stacked, sheets for stacking in and to a pile are traditionally connected to one another and wound on a reel. From the reel, the sheets, in the form of a continuous web, are conveyed into a cutting device which cuts them to a suitable size for individual sheets. After said cutting, the sheets are conveyed to a stacking arrangement which makes it possible for them to be stacked on one another in a single process. The stacking arrangement is so arranged that the sheets are first placed mutually in line on a conveyor belt which carries them to a stacking region. The sheets are placed on the conveyor belt such that a rear edge of each sheet is overlapped by a front edge of a following sheet. Having the sheets thus mutually overlapping makes it possible for them to be stacked on one another without becoming jammed. This is because each following sheet slides over, and will thus be placed on top of, the sheet preceding it.
European patent application EP-0192211-A2 refers to an arrangement in which sheets are placed on a conveyor belt. The sheets in EP-0192211-A2 are placed on the conveyor belt such that a rear edge of each sheet is overlapped by a front edge of a following sheet. A problem with EP-0192211-A2 is that it cannot handle thin sheets which are not stiff enough. If a sheet is too thin or not stiff enough, the result in EP-0192211-A2 is that when a sheet has to be moved from the conveyor belt to the arrangement for the formation of a stack of sheets, the front edge of the sheet will deflect downwards at the transition between the conveyor belt and the stack, with the result that the sheet is damaged and the stacking process has to be interrupted.
British patent specification GB-985227 refers to variants of an arrangement comprising a downpresser which presses down the rear edge of a sheet which is being transferred from a conveyor belt to another conveyor belt which moves at a slower speed. The fact that the downpresser pushes the rear edge down makes it possible for the front edge of a following sheet to overlap the pressed-down rear edge of the preceding sheet. A problem with that embodiment is that the downpresser is movable and rotatable. Such a movable element runs quite a large risk of disintegrating, thereby possibly resulting in the whole arrangement disintegrating. A further problem with the downpresser is that it may leave impressions in the sheet pressed down.
A problem with the inventions according to EP-0192211-A2 and GB-985227 is that they are not configured to be able to handle thin sheets but only so-called normal sheets, e.g. sheets with paper thickness corresponding to usual traditional writing paper. This means that sheets thinner than such writing paper which are used in the inventions according to EP-0192211-A2 and GB-985227 will become jammed, with consequent interruption of the sheet stacking processes.